One of the stars who doesn’t return, however, is Lily James, who played Lady Rose MacClare.

Downton creator Julian Fellowes explained to EW: “Lily is now a big star, and it would’ve been incredibly difficult for her to find time in her schedule to come and play essentially a supporting role in Downton when her career was in a different place when she was with us.”

He decided: “In the end, we all felt it was better to leave her in America.”

Neame continued: “Technically, she was only a recurring character in the final season. She came in and made some visits in a couple of episodes, but her story ended at the end of the fifth season when she went off to America.”

He added: “We knew we had to focus on the very core characters because there are not very many movies with 20 leading characters, and the dynamic of the TV series was that all these characters were treated equally.

“That’s one thing when you’ve got 10 or 11 hours of TV drama; another thing when it’s a two-hour movie. We had to be quite disciplined about focusing on the really central characters.”

Lily James commented last year: “My character Rose moved off to New York, so it would be far fetched to bring her back.

“I would have loved to have come back for a scene, but for a movie, it can’t be like a Christmas special and it needs to be a focused story-line. There was simply no space for Rose.”